Homocentrograph



16, 1966 CHlNG-YUAN NEOU 3,266,154

HOMOCENTROGRAPH Filed Feb. 25, 1966 INVENTOR.

BY /Z.,w

United States Patent 3,266,154 HOMUCENTROGRAPH Ching-Yuan Neon, 211Louisiana Ave., Bridgeport, Conn. Filed Feb. 23, 1966, Ser. No. 529,3311 Claim. (Cl. 33-77) This invention relates to a mechanical device tofacilitate the precision drawing or aligning of lines toward a distantcommon point lying beyond the drawing area.

The primary object is to facilitate the drawing of perspective lines,perspective spacing and measurement involving distant vanishing points,shadow lines cast by a remote light, etc.

A second object is to facilitate the graphical kinematic analysis whenthe instantaneous centers lie far away.

The third object is to align moving sources of light beams, cameras,reflectors, etc. to a designated spot.

In the drawings wherein like reference numbers indicate like parts.

FIG. 1 is a pictorial showing of the perspective geom etry of aparallelpiped.

FIG. 2 is a plan view of the homocentrograph.

FIG. 3 is a diagrammatic showing of the underlying principle of thehomocentrograph.

FIG. 4 is a fragmentary view of the cross-section of the center slideron the leg of the T-section.

FIG. 5 shows a marking device on the perspective arm for drawingperspective lines.

FIG. 6 is a diagrammatic showing of the geometry for aligning thehomocentrograph in a new position above the horizon line to a distantvanishing point.

FIG. 7 shows a clamp for holding the T-section in fixed position in thedrawing area.

In perspective drawings, all parallel lines displaced angularly from thepicture plane converge to a common point known as the vanishing point asthey proceed off into the distance. FIG. 1 shows a parallelpipedabcdefgh whose edged ab, ed, ef, and gh tend to converge to the rightvanishing point (VPR) on the horizon line (HL) or eye level; and edgesad, be, jg, and eh to the left vanishing point (VPL) on the same horizonline. When the vanishing points lie beyond the drawing area, drawing ofprecision perspective lines become very difiicult. The present inventionis a mechanical aid to establish the remote vanishing points (FIG. 2).

The homocentrograph consists mainly of a T-section having a bar 2, aperpendicular leg 3, an expandable zigzag linkage 4, a cross-bar 5, anda perspective arm 6. The lower edge ab of the bar 2 may be set tocoincide with the horizon line or one of the existing perspective lines.The zigzag linkage has its one end hinged on a pin 7, the intersectingpoint of the line ab and the centerline cd of the leg 3, and the otherend attached to a pin 9 on the center slider 8 (FIG. 4) which rides onthe leg and has side projections to slidably fit into the grooves in thesides of the leg 3. The graduated cross-bar 5 straddles across the leg 3and has two short slots to receive the two side pins 10 of the zigzaglinkage. The two guide posts 14- and 16 on the crossbar 5 are movableand can be held stationary at predetermined distances from thecenter-line cd by turning the pins and 17 which have threaded portionsin the guide posts 14 and 16. The perspective arm 6 has a narrow slot toengage the pins 9 and 15. Movement of the center slider 8 along the leg3 will cause a movement in the zigzag linkage which in turn drags thecross-bar along the leg. Differential motions of the pins 9 and 15result in translation as well as rotation of the perspective arm whichwill point at all times to the intersecting point of the extended lineof ab and the centerline of the perspective arm. A light perspectiveline can now be drawn by pushing down a marking device 3,266,154Patented August 16, 1966 18 against the spring in its holder 19 on theperspective arm (FIG. 5) while moving the perspective arm guided by thepin 9 and 15, or by moving a marking device in the slot of theperspective arm.

The principle of this invention can be explained as follows: a lineskeleton of the homocentrograph of FIG. 2 is shown in FIG. 3 in which Aand B represent pins 9 and 15 respectively and P is the right vanishingpoint VPR. Since the two triangles AGB and ACP are similar, we have ButG5 is a multiple of E, i.e. FZ=n1GZ (11:6 in

The foregoing equation indicates that for a fixed distance @E, theperspective lines always intersect the extension line of ab at adistance of n53, independent of the posi tion of the center slider A orthe perspective arm AB. Thus, by adjusting the distance 65 of the pin 15on the cross-bar, one can establish a desired vanishing point outsidethe drawing area for drawing perspective lines within.

It is quite obvious that if the homocentrograph is moved to a new areaand so positioned that the line ab and the center line of theperspective arm coincide with any two of the existing perspective lines,the perspective arm will remain aligned to P (FIG. 3). Also, if theperspective arm is held stationary and the T-section is moved, linesdrawn along the lower edge ab of the bar 2 become perspective linesconverging toward P. This technique may be used to draw perspectivelines close to the horizon line.

To draw perspective lines above the horizon line, a new reference lineAB' may be drawn (FIG. 6) which is the mirror image of the perspectiveline AB with respect to the horizon line. The homocentrograph can now bemoved and so positioned so that its line ab and the centerline of theperspective arm coincide with line AB' and the horizon linerespectively. On fixing the T-section in this new position, the centerslider 8 can be moved to draw new perspective lines.

If the cross-bar 5 in FIG. 2 is placed to engage the two pins 11 on thezigzag linkage 4 and the perspective arm pivoted on the pin 12, theperspective arm can be made to point to the same vanishing point,provided the pin 15 is held at a distance of one fourth of I on thecross-bar (FIG. 3).

To draw perspective lines converging to the left vanishing point (VPL),the perspective arm can simply be switched to have its slot engage thepin 17 on the guide post 16 at a predetermined distance from ca. Byproperly adjusting, positioning and orientating, the homocentrograph canbe used to establish vertical vanishing points or any points ofconvergence.

To hold the T-section in a fixed position within the drawing area, thebar 2 of the homocentrograph may be fixed directly to the drawing boardby using thumb nails in the holes provided in the bar 2 or secured to adrafting machine in a locked-in position. A simple fixture as shown inFIG. 7 may also be used. The U-shaped clamp 20 together with the bar 21in its provided slot can be fixed onto the drawing 'board 25 by a capscrew 23. The bar 22 can be locked up at any angle with respect to thebar 21 by the cap screw 24. The homocentrograph can thus be held in afixed position by inserting the two pins 14 in the bar 2 into the holes26 in the bar 22.

The homocentrograph may also be employed to a great advantage tofacilitate the perspective spacings and measurement involving remotevanishing points, the drawing of long shadows of objects cast by adistant light source, locating of unreachable instantaneous centers ingraphical kinematic analysis, etc.

In addition to the various applications in graphics, the homocentrographmay as well be used to align cameras, reflectors, etc. mounted on theperspective arm so that they will automatically face the same targetobject as they are moved.

Although several embodiments of the invention have been illustrated anddescribed, it is to be understood that the invention is not limitedthereto. As various changes in the construction, arrangement andapplications may be made without departing from the spirit of theinvention, as will be apparent to those skilled in the art, referencewill be had to the appended claim for a definition of the limits of theinvention.

The invention is hereby claimed as follows:

A device for establishing distant points of convergence to facilitatethe perspective drawing, graphical analysis, the aligning of movingobjects to a designated spot, and etc.; comprising a T-section, a zigzaglinkage having one end attached to the intersecting point of the loweredge of the bar of the said T-section and the centerline of its leg andthe other end attached to a pin on a center slider to be moved along thesaid centerline of the said leg, a graduated cross-bar riding on thesaid leg with slots to receive pins on the said zigzag linkage andhaving adjustable guide posts held at predetermined distances from thecenterline of the said leg, perspective arm having slot to engage pinson the said guide posts and the said center slider, means for drawingperspective lines along the said perspective arm.

No references cited.

LEONARD FORMAN, Primary Examiner.

